Moisture curable polyurethane coatings are extensively used as commercial and industrial protective and/or decorative coatings. Polyurethane coatings, known in the industry as one of the toughest coatings available, are routinely applied as protective coatings on exterior walls of buildings, industrial machinery, military equipment and vehicles, commercial and passenger vehicles, and any other surface requiring a protective coating. Moisture curable polyurethane systems are also used extensively as sealants and adhesives.
Moisture curing polyurethane coating systems typically include a polyisocyanate or prepolymer component which reacts with atmospheric water at room temperature to form useful films. These systems also include pigments, organic solvents, and a variety of adjuvant components, e.g., surface active agents, dispersants, diluents, and fillers. Since the polyisocyanate component reacts with even trace amounts of moisture, extreme care must be taken so that the polyisocyanates do not contact water until they are applied to a surface to be coated. Water is, however, unintentionally and unavoidably introduced into the formulation process in the form of dissolved water in solvents, adsorbed and absorbed moisture on the surfaces of fillers and pigments, and atmospheric moisture. Subsequent reaction of the water with the polyisocyanate component of the system results in an irreversible reaction which will harden the product, making it unusable before it can be applied to the surface to be coated. This water must be removed in order to produce an acceptable product. The existing methods for preparing color-pigmented moisture curable polyurethane coatings require expensive equipment to dry the pigments, solvents, and fillers. In the alternative, moisture scavenging agents are added to the coating preparation or are added to the pigments, solvents and other raw materials prior to or during preparation of the coating.
One group of moisture scavenging compounds are the molecular sieves. Molecular sieves adsorb water into their pores, thereby binding the water and preventing it from reacting with the polyisocyanate component. An example of a molecular sieve is sodium potassium aluminosilicate, available from the Mobay Corp., Pittsburgh, Pa., under the tradename designation Baylith L Powder. One disadvantage of using molecular sieves is that they reduce the gloss of the cured coating. Another disadvantage of molecular sieves is that they will sometimes plasticize or embrittle the cured coating.
A second group of water scavenging agents widely used to prevent moisture contamination of moisture curable polyurethane coating systems is the monomeric isocyanates. A typical monomeric isocyanate, such as p-toluenesulfonyl isocyanate (Vanchem, Inc. Lockport, Conn.), reacts with water to generate carbon dioxide and the corresponding sulfonamide, e.g., p-toluenesulfonamide. The carbon dioxide diffuses from the pigment grind during the dehydration phase as carbon dioxide gas. A disadvantage of monomeric isocyanates is that they are harmful if swallowed, inhaled, or absorbed through the skin and are extremely corrosive to the tissues of the mucous membranes, upper respiratory tract, and skin.
There is a need for a moisture scavenger which efficiently, cost effectively, and safely removes water from moisture curable coating systems and from any other preparation where residual water is a problem, without seriously detracting from the performance of the cured coating.
Formaldehyde is a raw material frequently used in polymeric systems including phenol-formaldehyde, urea-formaldehyde, and melamine-formaldehyde. Exposure to formaldehyde vapors in the workplace is stringently controlled by the use of formaldehyde scavengers. Formaldehyde scavengers capture formaldehyde and hold it in a form having significantly lower formaldehyde vapor pressure. Products such as textiles and plywood typically contain a formaldehyde scavenger to reduce free formaldehyde levels without changing the physical properties of the products. Known formaldehyde scavengers include nitroparaffins such as nitromethane (NM.TM.), nitroethane (NE.TM.), 1-nitropropane (NiPar S-10.TM.) and 2-nitropropane (NiPar S-20.TM.), and amino alcohols such as 2-amino-2-methyl- 1-propanol (AMP.TM.), 2-amino-2-ethyl-1,3-propanediol (AEPD.RTM.) and tris(hydroxymethyl)aminomethane (TRIS AMINO.RTM.), which are manufactured by ANGUS Chemical Company.
There is a need for a formaldehyde scavenger which efficiently, cost effectively, and safely removes formaldehyde from polymeric systems and from any other preparation where free formaldehyde is a problem, without seriously detracting from the performance or physical properties of the system.
Corrosion is often prevalent in engine cooling systems. Metals such as copper, iron, steel, aluminum, magnesium and the like are often exposed to high temperatures, pressures and flow rates in these cooling systems. These conditions corrode metal forming corrosion products which may cause engine overheating or engine failure. Lightweight metals in engine components such as aluminum and magnesium are subject to pitting of radiator tubes, crevice corrosion at hose connections, and deposit corrosion from deposition of corrosion products. Corrosion inhibitors are added to antifreeze/coolant compositions and functional fluids which contact metal to prevent and control corrosion in engine cooling systems and other machinery. U.S. Pat. No. 4,282,108 describes oxazolidine derivatives which are used as chelants, anti-copper-corrosion additives and frictional modifiers in automatic transmission fluid, and oxidation inhibitors in middle distillate fuels.
There is a need for a corrosion inhibitor which effectively reduces the incidence of corrosion of metals or alloys, and which may be applied to a surface of a metal or alloy or may be incorporated in a functional fluid which contacts a surface of a metal or alloy.
Coating, adhesive or sealant formulations also may include rheological modifiers to reduce viscosity, disperse pigments, and improve solvency, flow and leveling. Formulations which do not contain rheological modifiers may exhibit a rapid increase in viscosity for a relatively small increase in solids content. The increased viscosity causes the formulation to set quickly resulting in striations in the formulation. Addition of a rheological modifier enables the formulation to flow into a smooth layer before it sets. Conventional rheological modifiers include polyethylene glycols such as Carbowax and polyethylene oxides such as Polyox.
There is a need for a rheological modifier to reduce viscosity, reduce volatile organic content, disperse pigments, and improve the solvency, flow and leveling properties of a coating, adhesive or sealant.